What is called a lateral double-diffused field-effect transistor has traditionally been known as one of transistors which operate at the time of a relatively high voltage being applied.
With a lateral double-diffused field-effect transistor, an n-well diffusion layer is formed, for example, in a p-type substrate, a p-body diffusion layer is formed in the n-well diffusion layer, and a drain diffusion layer and a source diffusion layer are formed in the n-well diffusion layer and the p-body diffusion layer respectively. In addition, a gate electrode is formed over the p-type substrate between the drain diffusion layer and the source diffusion layer and over the n-well diffusion layer and the p-body diffusion layer. With such a lateral double-diffused field-effect transistor a technique for adjusting the length of or impurity concentration in a region (drift region) between a p-body diffusion layer and a drain diffusion layer, a technique for forming a local oxide film over a drift region, and the like are also known. Furthermore, a structure in which a source diffusion layer is surrounded by a frame-like drain diffusion layer and in which a frame-like gate electrode is formed over a p-type substrate between the source diffusion layer and the frame-like drain diffusion layer and over an n-well diffusion layer and a p-body diffusion layer is also known as a lateral double-diffused field-effect transistor.    Japanese Laid-open Patent Publication No. 2008-091689    Japanese Laid-open Patent Publication No. 2007-067181
With a lateral double-diffused field-effect transistor, however, it may be impossible to ensure desired breakdown voltage, depending on the structure. For example, it may be impossible to ensure desired breakdown voltage, depending on the placement of a diffusion layer in a substrate and a gate electrode. This may cause a deterioration in the performance of a transistor having such a structure and an apparatus including a transistor having such a structure.